The absolute minimum things that I need to know about Helm

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I am learning about helm. It is a package manager for Kubernetes.

This documentation page provided me a good starting point: https://helm.sh/docs/topics/architecture/ and then I roamed around the docs gathering the below notes.

The latest helm version as of writing this notes is v3.10.3.

(If something is wrong, feel free to suggest a fix as a pull request here)

  • basics
    • chart - kubernetes yaml definitions to run the app
    • repository - collection of charts
    • release - running instance of a chart. Two releases of same chart could be running at the same time in a kubernetes cluster (example: two redis instances used by different services)
  • helm repo add [name] [url]
    • add a repo to use the charts inside it.
  • helm repo update
    • updates the list of charts available in the added repositories

  • versioning

    • a chart seem to contain two versions
      • chart version
      • application version

    • example: vault’s chart and app versions

      NAME CHART VERSION APP VERSION DESCRIPTION
      hashicorp/vault 0.23.0 1.12.1 Official HashiCorp Vault Chart

  • helm search hub [query]

    • searches for charts in artifact hub
  • helm search repo [query]
    • searches for charts in locally added repositories

  • helm install [release_name] [chart]

    • You can also use helm install [chart] --generate-name if you wish to generate a release name automatically (example: redis-TIMESTAMP)
    • the order in which the kubernetes resources mentioned in the chart are installed is document at https://helm.sh/docs/intro/using_helm/#helm-install-installing-a-package

    • Helm does not wait until all of the resources are running before it exits. Many charts require Docker images that are over 600M in size, and may take a long time to install into the cluster.

    • Use helm status to get the state of the install

  • helm show values [chart]
    • You can customize the values that are configured in a chart before deploying a release
    • This command will help you understand what values are available in a chart that could be modified
  • helm install -f values.yaml [release_name] [chart]
    • the vaules in values.yaml file will override the config values
  • Other methods of installing charts
    • A chart repository
    • A local chart archive (helm install foo foo-0.1.1.tgz)
    • An unpacked chart directory (helm install foo path/to/foo)
    • A full URL (helm install foo https://example.com/charts/foo-1.2.3.tgz)

  • helm upgrade [release_name] [chart]

    • When a new version of a chart is released, or when you want to change the configuration of your release, you can use the helm upgrade command.

  • helm get values [release_name]

    • Useful in getting the values used in a release

  • helm rollback [release_name] [revision]

    • The above rolls back our happy-panda to its very first release version. A release version is an incremental revision. Every time an install, upgrade, or rollback happens, the revision number is incremented by 1. The first revision number is always 1.

  • helm list

    • Lists all the releases
  • helm history [release_name]
    • Lists all the revisions for a release
    • You can then use helm get values [release_name] --revision NUMBER to get the values used in a particular revision
  • Helpful options during install/upgrade/rollback
    • –timeout
      • A Go duration value to wait for Kubernetes commands to complete. This defaults to 5m0s.
    • --wait: Waits until all Pods are in a ready state, PVCs are bound, Deployments have minimum (Desired minus maxUnavailable) Pods in ready state and Services have an IP address (and Ingress if a LoadBalancer) before marking the release as successful. It will wait for as long as the --timeout value. If timeout is reached, the release will be marked as FAILED
  • helm uninstall [release_name]
    • use --keep-history if you wish to the uninstalled release to show up in helm list --all
  • helm create [name]
    • for creating a new chart
  • helm package [folder_name]
    • should output a *.tgz file (known as chart archive, I guess)